Future.ts

class Future<A> {

  constructor(public promise: Promise<A>) { }

  static value<A>(arg: A) {
    return new Future(
      new Promise<A>(resolve => resolve(arg))
    )
  }

  map(callback: (p: A) => any): Future<any> {
    const prom = new Promise<any>((resolve, reject) => {
      this.promise.then(x => {
        resolve(callback(x))
      });
    });
    return new Future(prom)
  }
}